From the article, there’s a difference between copyright and trademark protection, so this is how Steamboat Willie will be available for public use:
Due to the company’s trademark on later iterations of Mickey Mouse, you won’t see Mickey serving as another company’s mascot either, Lee said
“Just like the Nike Swoosh and Tiffany Blue, Disney owns Mickey,” Lee said. “It cannot be used in that recognizable way for advertising.”
Despite the copyright expiration, adopting Disney’s famous mouse may prove “a tricky thing to do,” Lee said. “If they feel that you’re diluting their brand, if they feel like you’re tarnishing their brand, that’s problematic and they’re going to sue you.”
However, some exceptions exist to Disney’s tight grip on its affable mouse. Even the more modern version of Mickey Mouse can be shown for educational purposes, satire or parody, Lee said.